Energy Conservation Building Code User Guide for India 9788190902533

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ENERGY CONSERVATION BUILDING CODE (ECBC) USER GUIDE

July 2009

Energy Conservation Building Code User Guide

© 2009 Bureau of Energy Eficiency

Published by: Bureau of Energy Eficiency 4th Floor, Sewa Bhawan, R. K.Puram, New Delhi, India Developed by: USAID ECO-III Project International Resources Group 2, Balbir Saxena Marg, Hauz Khas, New Delhi, India

No portion (graphics or text) of this report may be reproduced, translated, or transmitted in any form or manner by any means—including but not limited to electronic copy, photocopy, or any other informational storage and retrieval system without explicit written consent from Bureau of Energy Eficiency, New Delhi.

All rights reserved Printed in New Delhi, India ISBN No. 978-81-909025-3-3 July 2009

This report is made possible by the generous support of the U.S. Government through the ECO-III Project to the Indian Government. The views expressed in this report do not necessarily relect the views of partner countries – United States of America and India – or the United States Agency for International Development.

USAID ECO-III Project The Energy Conservation and Commercialization (ECO) Program was signed between the Government of India (GOI) and USAID in January 2000 under a bilateral agreement with the objective to enhance commercial viability and performance of Indian energy sector and to promote utilization of clean and energy-eficient technologies in the sector. Following the enactment of the Energy Conservation Act 2001, ECO-I Project supported GOI in the establishment of the Bureau of Energy Eficiency (BEE). Support to BEE was provided to set up procedures and authorities, establish ofice facilities and assist in several activities leading to the development of BEE’s Action Plan including thrust area such as the development of an energy auditor certiication program. ECO-II Project provided BEE with necessary technical assistance and training support to implement three thrust areas of the Action Plan. The irst area was to develop the Energy Conservation Building Codes (ECBC) for the ive climatic zones of India, the second was to support Maharashtra Energy Development Agency in developing strategies for energy conservation and implementation of selected programs, and the third area focused on implementing a pilot DSM program to replace incandescent lamps with CFLs in the state of Karnataka in partnership with BESCOM. Since November 2006, International Resources Group (IRG), with support from its partners IRG Systems South Asia, Alliance to Save Energy and DSCL Energy Services, other partner organizations and consultants has been implementing the ECO-III Project by working closely with BEE, Gujarat Energy Development Agency, and Punjab Energy Development Agency. ECBC User Guide has been produced to assist Government of India in the implementation of ECBC, which was launched by Ministry of Power in May 2007. It is hoped that this document will help in creating awareness and enhancing understanding about the ECBC. ECO-III Project has developed Tip Sheets and Design Guides in the past to help in the ECBC implementation efforts. More information as well as electronic copies of all the publications can be accessed at www.eco3.org.




Foreword The Energy Conservation Act, 2001(52 of 2001) empowers the Central Government under Section 14(p) read with Section 56(2)(l) to prescribe Energy Conservation Building Code (ECBC). The Code deines norms and standards for the energy performance of buildings and their components based on the climate zone in which they are located. Under the leadership of Bureau of Energy Eficiency (BEE), a Committee of Experts inalized ECBC in consultation with various Stakeholders in 2007, with an overall purpose to provide minimum requirements for the energy-eficient design and construction of buildings. ECBC covers building envelope, heating, ventilation, and air conditioning system, interior and exterior lighting system, service hot water, electrical power system and motors. In May 2007, the Ministry of Power, Government of India formally launched the ECBC for its voluntary adoption in the country. Since then, BEE has been promoting and facilitating its adoption through several training and capacity building programmes. BEE is also monitoring implementation of ECBC through the ECBC Programme Committee (EPC). EPC also reviews periodically the inconsistencies and comments on ECBC received from various quarters. In this context, BEE in consultation with EPC and support from USAID ECO-III Project brought out a revised version of ECBC in May 2008. During the capacity building effort, a need was clearly felt to provide additional guidance to design and construction professionals on the rationale behind the ECBC speciications and provide explanations to the key terms and concepts governing these speciications so that people are able to comprehend ECBC in a better way. Considering this growing need for developing a better understanding of ECBC in the country, the ECBC User Guide has been prepared under the USAID ECO-III Project in close partnership with BEE. The document aims to guide and assist the building designers, architects and all others involved in the building construction industry to implement ECBC in real situations. The document is written both as a reference and as an instructional guide. It also features examples, best practices, checklists, etc. to direct and facilitate the design and construction of ECBC-compliant buildings in India. I am happy to note that the ECBC User Guide Development Team has made a concerted effort to provide all the information, especially minimum performance standards that buildings need to comply with, in one place. Consequently, it is my hope that users of ECBC trying to show compliance through the prescriptive path will ind it easier to do so through the guidance provided in the document. The ECBC User Guide also provides additional guidance on the Whole Building Performance method by making references to international publications that are widely used by the building design community. I thank the entire ECBC User Guide Development Team, led by Dr. Satish Kumar, for its extensive efforts in bringing out this document. I would like to express my sincere appreciation to the USAID for providing this technical assistance under the ECO-III Project and to the International Resources Group for spearheading this team effort.

17th July, 2009







(Dr. Ajay Mathur)

ECBC User Guide Development Team Satish Kumar, Team Leader IRG, USAID ECO-III Project •

Aleisha Khan, Alliance to Save Energy

•

Anurag Bajpai, IRG, USAID ECO-III Project

•

G. S. Rao, Team Catalyst

•

Jyotirmay Mathur, Malviya National Institute Technology

•

Laurie Chamberlain, International Resources Group (IRG)

•

P. C. Thomas, Team Catalyst

•

Rajan Rawal, Center for Environmental Planning and Technology

•

Ravi Kapoor, IRG, USAID ECO-III Project

•

Surekha Tetali, International Institute of Information Technology

•

Vasudha Lathey

•

Vishal Garg, International Institute of Information Technology

Acknowledgements Energy Conservation Building Code (ECBC) User Guide, developed by the USAID ECO-III Project in association with Bureau of Energy Eficiency (BEE) aims to support the implementation of ECBC. I would like to thank Dr. Archana Walia, Project Manager, and Mr. S. Padmanaban of USAID for their constant encouragement and steadfast support during the development process. I would like to acknowledge the tremendous support and encouragement provided by Dr. Ajay Mathur, Director General, and Mr. Sanjay Seth, Energy Economist of BEE in the preparation of the Guide. A substantial undertaking of this nature would not have been possible without the extremely valuable technical contribution provided by the Development Team of ECBC User Guide especially Ms. Vasudha Lathey, Ms. Aleisha Khan of Alliance to Save Energy (ASE), Dr. Vishal Garg and Ms. Surekha Tetali of International Institute of Information Technology (IIIT), Prof. Rajan Rawal of Center for Environmental Planning and Technology (CEPT), Dr. Jyotirmay Mathur of Malviya National Institute Technology (MNIT), Mr. P. C. Thomas and Mr. G. S. Rao of Team Catalyst. I would like to acknowledge the assistance that the Development Team received from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Inc., USA. The 90.1 User Manual, ANSI/ ASHRAE/IESNA Standard 90.1-2004, provided us with a robust framework and a sound technical reference during the development of the ECBC User Guide. I am also thankful to Ms. Meredydd Evans of Paciic NorthWest National Laboratory (PNNL), and to Saint Gobain, DuPont, ASAHI-India, and Dr. Mahabir Bhandari (DesignBuilder) for providing inputs on many iterations of this document. I would like to convey my special thanks to the ECO-III Project Team – Mr. Ravi Kapoor for his substantial technical contribution to the development of the entire document, Mr. Anurag Bajpai for his tireless efforts in coordinating inputs from the Development Team members, and Ms. Meetu Sharma for her persistence efforts to prepare the graphics and desktop layout of multiple iterations of the document. Without the perseverance and discipline of ECO-III Project Team this work would not have been possible. I also like to thank Ms. Laurie Chamberlain of International Resources Group (IRG) HQ for assisting us in carrying out technical editing of this document.

17th July, 2009

(Dr. Satish Kumar) Chief of Party, USAID ECO-III Project International Resources Group

How to Use This Guide The ECBC User Guide follows the same structure as the Energy Conservation Building Code. Consequently, Chapters 1 through 8 and Appendix A through G are identical to the ECBC chapters and the sections within each chapter also follow the ECBC. Appendix B provides detailed guidance on the Whole Building Performance method. Assumptions that can be standardized have been included to reduce the chances of gamesmanship and to create a framework that would allow for “apples to apples” comparison across different projects while creating simulation models for Standard and Proposed Design. Appendix E is about Climate Zones in India. This appendix provides a summary of each of the ive climate zones and another table that provides a listing of major Indian cities along with its climatic zone. A new Appendix H has been included that provides a comparison of International Building Energy Standards. Apart from comparing some of the technical speciications, this appendix also provides the different approaches taken by countries to check code compliance and enforcement. It is hoped that this section will provide some ideas to the policy makers on how to make ECBC compliance mandatory so that minimum energy eficiency performance can be met by buildings coming under the scope of ECBC. The ECBC User Guide has been designed in an easy to understand format. The document uses a consistent format and provides guidance at the following three levels:

a) Text that is shown in Blue This text is a direct excerpt from the ECBC document and is likely to serve as an anchor for many of the guidance text and examples included in different chapters. Users interested in showing ECBC compliance should pay close attention to the text drawn from ECBC and shown in blue. Examples of ECBC text and ECBC table are reproduced below for guidance: The Code is applicable to buildings or building complexes that have a connected load of 500 kW or greater or a contract demand of 600 kVA or greater. Window Wall Ratio

Minimum VLT

0 - 0.3

0.27

0.31-0.4

0.20

b) Boxed Text showing Tips, Frequently Asked Questions (FAQ), Examples, etc. The Boxed Text provides guidance to the users for better understanding of ECBC concepts and ECBC applicability in different situations. An example of Boxed Text is shown below:

Box 1-A: : Role of Climate Zone The ECBC building envelope requirements are based on the climate zone in which the building is located. ECBC deines ive climate zones (hot-dry; warm-humid; composite; temperate; cold), which are distinctly unique in their weather proiles (Appendix E). Based on the characteristics of climate, the thermal comfort requirements in buildings and their physical manifestation in architectural form are also different for each climate zone

c) Normal text in black This type of text forms the core of the ECBC User Guide and provides overall guidance on how best to understand and apply ECBC.

Table of Contents USAID ECO-III Project

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Foreword

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ECBC User Guide Development Team .

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Acknowledgements .

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How to Use This Guide .

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1.

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3.

2.1

Applicable Building Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.2

Exemptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.3

Safety, Health, And Environmental Codes Take Precedence. . . . . . . . . . . . . . . . 2

2.4

Reference Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Administration and Enforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1

Compliance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1.1 Mandatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1.2 New Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1.3 Additions to Existing Buildings . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.4 Alterations to Existing Buildings . . . . . . . . . . . . . . . . . . . . . . . 5

3.2

Compliance Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.3

Administrative Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.4

Compliance Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.4.2

4.

Supplemental Information . . . . . . . . . . . . . . . . . . . . . . . . 11

Building Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.2

Mandatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2.1 Fenestration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2.2 Opaque Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2.3 Building Envelope Sealing . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.3

Prescriptive Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3.1 Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3.2 Cool Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.3.3 Opaque Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.3.4 Vertical Fenestration . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.3.5 Skylights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.4 5.

Building Envelope Trade-Off Option . . . . . . . . . . . . . . . . . . . . . . . 32

Heating, Ventilation and Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . . 33

5.1

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

5.2

Mandatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 5.2.1 Natural Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 5.2.2

Minimum Equipment Eficiencies . . . . . . . . . . . . . . . . . . . . . 38

5.2.3 Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 5.2.4 Piping and Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 5.2.5 System Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 5.2.6 Condensers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 5.3

Prescriptive Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 5.3.1 Economizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.3.2 Variable Flow Hydronic Systems . . . . . . . . . . . . . . . . . . . . . . 50

6.

Service Water Heating and Pumping . . . . . . . . . . . . . . . . . . . . . . . . . . 52 6.1

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6.2

Mandatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 6.2.1 Solar Water Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 6.2.2 Equipment Eficiency . . . . . . . . . . . . . . . . . . . . . . . . . . 54 6.2.3 Supplementary Water Heating System . . . . . . . . . . . . . . . . . . . . 55 6.2.4 Piping Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.2.5 Heat Traps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 6.2.6 Swimming Pools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 6.2.7 Compliance Documentation . . . . . . . . . . . . . . . . . . . . . . . . 57

7.

Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 7.1

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

7.2

Mandatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 7.2.1 Lighting Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 7.2.2 Exit Signs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 7.2.3 Exterior Building Grounds Lighting . . . . . . . . . . . . . . . . . . . . . 64

7.3

Prescriptive Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 7.3.1 Interior Lighting Power . . . . . . . . . . . . . . . . . . . . . . . . . . 65 7.3.2 Building Area Method . . . . . . . . . . . . . . . . . . . . . . . . . . 65 7.3.3 Space Function Method . . . . . . . . . . . . . . . . . . . . . . . . . . 66 7.3.4 Installed Interior Lighting Power . . . . . . . . . . . . . . . . . . . . . . 67 7.3.5 Exterior Lighting Power . . . . . . . . . . . . . . . . . . . . . . . . . . 68

8.

Electrical Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.1

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

8.2

Mandatory Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.2.1 Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.2.2 Energy-Eficient Motors . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.2.3 Power Factor Correction . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.2.4 Check-Metering and Monitoring . . . . . . . . . . . . . . . . . . . . . . 78 8.2.5 Power Distribution Systems . . . . . . . . . . . . . . . . . . . . . . . . 78 9.

APPENDIX A: ECBC Deinitions, Abbreviations and Acronyms . . . . . . . . . . . . . . A.1 9.1

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A.1

9.2

Deinitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A.1

9.3

Abbreviations and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . A.12

10. APPENDIX B: Whole Building Performance Method . . . . . . . . . . . . . . . . . . . B.1 10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B.1 10.1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B.1 10.1.2 Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B.2 10.1.3 Annual Energy Use . . . . . . . . . . . . . . . . . . . . . . . . . . . B.3 10.1.4 Trade-offs Limited to Building Permit . . . . . . . . . . . . . . . . . . . . B.3 10.1.5 Documentation Requirements . . . . . . . . . . . . . . . . . . . . . . . B.3 10.2 Simulation General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . B.3 10.2.1 Energy Simulation Program . . . . . . . . . . . . . . . . . . . . . . . . B.3 10.2.2 Climate Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . B.5 10.2.3 Compliance Calculations . . . . . . . . . . . . . . . . . . . . . . . . . B.5 10.3 Calculating the Energy Consumption of the Proposed Design and the Standard Design . . . . . B.6 10.3.1 The simulation model for calculating the Proposed Design and the Standard Design shall be developed in accordance with the requirements in Table 10.1 . . . . . . . . . . . B.6 11. APPENDIX C: Default Values for Typical Constructions . . . . . . . . . . . . . . . . . . C.1 11.1 Procedure for Determining Fenestration Product U-Factor and Solar Heat Gain Coeficient . . C.1 11.2 Default U-factors and Solar Heat Gain Coeficients for Unrated Fenestration Products . . . . C.2 11.2.1 Unrated Vertical Fenestration . . . . . . . . . . . . . . . . . . . . . . . C.2 11.2.2 Unrated Sloped Glazing and Skylights . . . . . . . . . . . . . . . . . . . . C.2 11.3 Typical Roof Constructions . . . . . . . . . . . . . . . . . . . . . . . . . . . C.2 11.4 Typical Wall Constructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . C.3 12. APPENDIX D: Building Envelope Tradeoff Method . . . . . . . . . . . . . . . . . . . D.1 12.1 The Envelope Performance Factor . . . . . . . . . . . . . . . . . . . . . . . . D.1 12.1.1 The envelope performance factor shall be calculated using the following equations. . . D.1 12.1.2 Overhang and Side Fin Coeficients . . . . . . . . . . . . . . . . . . . . . D.2 12.1.3 Baseline Building Deinition . . . . . . . . . . . . . . . . . . . . . . . . D.5 13. APPENDIX E: Climate Zone Map of India . . . . . . . . . . . . . . . . . . . . . . . E.1 13.1 Climate Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E.1 14. APPENDIX F: Air-Side Economizer Acceptance Procedures . . . . . . . . . . . . . . . . F.1 14.1 Construction Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.1 14.2 Equipment Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.1 15. APPENDIX G: ECBC Compliance Forms . . . . . . . . . . . . . . . . . . . . . . . G.1 15.1 Envelope Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G.1

15.2 Building Permit Plans Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . G.2 15.3 Mechanical Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G.3 15.4 Mechanical Permit Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . G.4 15.5 Lighting Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G.5 15.6 Lighting Permit Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . G.6 15.7 Whole Building Performance Checklist . . . . . . . . . . . . . . . . . . . . . . . G.7 16. APPENDIX H: Comparison Of International Building Energy Standards . . . . . . . . . . . H.1 17. APPENDIX I: References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I.1

List of Tables Table 4.1: Values of Surface Film Resistance Based on Direction of Heat Flow .

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. . 14

Table 4.2: Thermal Resistances of Unventilated Air Layers Between Surfaces with High Emittance .

. . 15

Table 4.3: Comfort Requirements and Physical Manifestations in Buildings .

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. . 19

Table 4.4: Roof Assembly U-Factor and Insulation R-value Requirements (ECBC Table 4.3.1) .

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. . 21

Table 4.5: Opaque Wall Assembly U-Factor and Insulation R-value Requirements (ECBC Table 4.2) .

. . 26

Table 4.6: Vertical Fenestration U-factor (W/m2·K) and SHGC Requirements (ECBC Table 4.3) . .

. . 26

Table 4.7: Defaults for Unrated Vertical Fenestration (Overall Assembly including Sash and Frame) - Table 11.1 of ECBC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Table 4.8: SHGC “M” Factor Adjustments for Overhangs and Fins (ECBC Table 4.4) . .

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Table 4.9: Minimum VLT Requirements (ECBC Table 4.5) .

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Table 4.10: Skylight U-Factor and SHGC Requirements (ECBC Table 4.6) . . .

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Table 5.1: Optimum Size/Number of Fans for Rooms of Different Sizes .

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. . 37

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Table 5.2: Chillers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Table 5.3: Power Consumption Ratings for Unitary Air Conditioners – Under Test Conditions .

. .

Table 5.4: Power Consumption Ratings for Split Air Conditioners – Under Test Conditions . .

. . . . 42

Table 5.5: Power Consumption Rating for Packaged air Conditioners-under test conditions

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. . 42 . . 42

Table 5.6: Insulation of Heating Systems . .

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Table 5.7: Insulation of Cooling Systems . .

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Table 5.8: Ductwork Insulation . .

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Table 5.9: Sample R-values for Duct Insulation Materials . . . . . . . . . . . . . . . . . . . . 45 Table 6.1: Standing Loss in Storage Type Electric Water Heaters .

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Table 6.2: Insulation of Hot Water Piping. . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Table 7.1: Interior Lighting Power- Building Area Method (ECBC Table 7.1) . .

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Table 7.2: Interior Lighting Power- Space Function Method (ECBC Table 7.2) . . . . . . . . . . . . 66 Table 7.3: Exterior Lighting Building Power (ECBC Table 7.3) . . . . . . . . . . . . . . . . . . 68 Table 8.1: Dry-Type Transformers (ECBC Table 8.1) . . . . . . . . . . . . . . . . . . . . . . 71 Table 8.2: Oil Filled Transformers (ECBC Table 8.2) . . . . . . . . . . . . . . . . . . . . . . 71 Table 8.3: Values of Performance Characteristic of Two Pole Energy-Eficient Induction Motors. . . . . 73 Table 8.4: Values of Performance Characteristic of 4 Pole Energy-Eficient Induction Motors. .

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Table 8.5: Values of Performance Characteristic of 6 Pole Energy-Eficient Induction Motors. .

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Table 8.6: Values of Performance Characteristic of 8 Pole Energy-Eficient Induction Motors. .

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Table 10.1: Modeling Requirements for Calculating Proposed and Standard Design . . . . . . . . . . B.7 Table 10.2: Standard Fan Brake Horsepower .

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Table 10.3: Type and Number of Chillers . .

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Table 10.4: Part-Load Performance for VAV Fan Systems . . . . . . . . . . . . . . . . . . . B.20 Table 10.5: HVAC Systems Map (Reproduced from ECBC 10.2) .

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Table 10.6: Electrically Operated Packaged Terminal Air Conditioners .

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Table 10.7: Building Energy Model Information. . . . . . . . . . . . . . . . . . . . . . . B.23 Table 11.1: Defaults for Unrated Vertical Fenestration (Overall Assembly including the Sash and Frame) . C.2 Table 11.2: Defaults for effective U-Factor for Exterior Insulation layers (under review) . . . . . . . . C.2 Table 11.3: Defaults for effective U-factor for Exterior Insulation Layers (under review) . . . . . . . . C.3 Table 12.1: Envelope Performance Factor Coeficients-Composite Climate (under review) .

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Table 12.2: Envelope Performance Factor Coeficients-Hot Dry Climate (under review) . . . . . . . . D.2 Table 12.3: Envelope Performance Factor Coeficients-Hot Humid Climate (under review)

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Table 12.4: Envelope Performance Factor Coeficients-Moderate Climate (under review) .

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Table 12.5: Envelope Performance Factor Coeficients-Cold Climate (under review) .

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Table 12.6: Overhang and Side Fin Coeficients . . . . . . . . . . . . . . . . . . . . . . . . D.3 Table 13.1: Classiications of Different Climate Zones in India . . . . . . . . . . . . . . . . . . E.2 Table 13.2: Climate Zone of the Major Indian Cities . . . . . . . . . . . . . . . . . . . . . . E.3

List of Figures Figure 3.1: Design Process for the Whole Building Performance Method . . . . . . . . . . . . . .

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Figure 3.2: The Building Design and Construction Process .

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Figure 4.1: Building Envelope .

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Figure 4.2: The Solar and Blackbody Spectrum . .

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Figure 4.3: Schematic Showing Three Modes of Heat Transfer . . . . . . . . . . . . . . . . . . 13 Figure 4.4: Typical Cavity Wall Construction .

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Figure 4.6: Heat Transfer (Conduction, Convection, & Radiation) and Iniltration Across a Window . . . . 17 Figure 4.7: Building Roofs . .

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Figure 4.8: Typical Insulation Techniques for RCC Roof Construction.

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Figure 4.9: Heat Transfer Through Roof

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Figure 4.10: Projection Calculation .

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Figure 4.11: Illustration to show U-factor, SHGC, and VLT .

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Figure 4.12: Skylight Installations .

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Figure 5.1: Acceptable operative temperature ranges for naturally conditioned spaces. .

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Figure 5.2: Economizer .

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Figure 6.1: Batch Collector Passive System . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Figure 6.2: Active Indirect System .

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Figure 6.3: Instantaneous Water Heater .

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Figure 6.4: Heat Trap Elements . .

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Figure 7.1: Relative Eficacy of Major Light Sources (Lumens/Watt) .

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Figure 7.2: Watts per Lighting System Eficiency .

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Figure 8.1: Transformer .

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Figure 8.2: Transformer loss vs % Load .

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Figure 8.3: Increase in eficiency (Percentage points) . . . . . . . . . . . . . . . . . . . . . . 76 Figure 8.4: Proile cutaway of an induction motor stator and rotor . . Figure 13.1: Climate Zone Map . .

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Purpose

1. Purpose purpose of Energy Conservation Building Code (ECBC) is to provide minimum requirements for Theenergy-eficient design and construction of buildings and their systems. The building sector represents about 33% of electricity consumption in India, with commercial sector and residential sector accounting for 8%and 25% respectively. Estimates based on computer simulation models indicate that ECBC-compliant buildings can use 40 to 60% less energy than conventional buildings. It is estimated that the nationwide mandatory enforcement of the ECBC will yield annual savings of approximately 1.7 billion kWh. The ECBC is expected to overcome market barriers, which otherwise result in under-investment in building energy eficiency. The ECBC was developed as a irst step towards promoting energy eficiency in the building sector. The ECBC (also referred to as “The Code” in this document) is the result of extensive work by the Bureau of Energy Eficiency (BEE) and its Committee of Experts. It is written in code-enforceable language and addresses the views of the manufacturing, design, and construction communities as an appropriate set of minimum requirements for energy-eficient building design and construction. For developing the Code, building construction methods across the country were reviewed and various energyeficient design and construction practices were evaluated that could reduce energy consumption in building. In addition, detailed life-cycle cost analyses were conducted to ensure that the Code requirements relect costeffectiveness and practical eficiency measures across ive different climate zones in India. While taking into account different climate zones, the Code also addresses site orientation and speciies better design practices and technologies that can reduce energy consumption without sacriicing comfort and productivity of the occupants. The ECBC User Guide (also referred to as “The Guide” in this document) has been developed to provide detailed guidance to building owners, designers, engineers, builders, energy consultants, and others on how to comply with the Code. It provides expanded interpretation, examples, and supplementary information to assist in applying ECBC during the design and construction of new buildings as well as additions and alterations to existing buildings. This Guide can also be used as a document by “authorities having jurisdiction” in the enforcement of the Code once it is made mandatory. The Guide follows the nomenclature of the Code. It is written both as a reference and as an instructional guide, and can be helpful for anyone who is directly or indirectly involved in the design and construction of ECBC-compliant buildings.

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Scope

2. Scope

T

he Code is applicable to buildings or building complexes that have a connected load of 500 kW or greater or a contract demand of 600 kVA or greater.

Generally, buildings or complexes having conditioned area of 1,000 m2 or more will fall under this category. The Code is presently under voluntary adoption in the country. This Code would become mandatory as and when it is notiied by the Central and State government in the oficial Gazette under clause (p) of §14 or clause (a) of §15 of the Energy Conservation Act 2001 (52 of 2001)

2.1 Applicable Building Systems The provisions of the Code apply to: • Building envelopes, except for unconditioned storage spaces or warehouses • Mechanical systems and equipment, including heating, ventilating, and air conditioning, (HVAC) • Service hot water heating • Interior and exterior lighting • Electrical power and motors Speciic compliance requirement of the above building components and systems are discussed in Chapter 4 through Chapter 8 of this Guide.

2.2 Exemptions The provisions of this Code do not apply to: • Buildings that do not use either electricity or fossil fuel • Equipment and portions of building systems that use energy primarily for manufacturing processes

2.3 Safety, Health, And Environmental Codes Take Precedence Where this Code is found to conlict with safety, health, or environmental codes, the safety, health, or environmental codes shall take precedence.

2.4 Reference Standards National Building Code (NBC) 2005 is the reference document/standard for lighting levels, HVAC, comfort levels, natural ventilation, pump and motor eficiencies, transformer eficiencies and any other building materials and system performance criteria. The National Building Code 2005 has also been used as a reference in this Guide. The Code is a dynamic document under continuous maintenance. Addenda, errata, and interpretations can be issued as and when necessary by the concerned authorities such as the Ministry of Power, the Bureau of Energy Eficiency, the state governments, etc. This Guide is consistent with ECBC 2007 (revised version, May 2008). Designers using this Guide should conirm if any addendum has been adopted in the Code by the Authority Having Jurisdiction before incorporating its requirements in the proposed building’s design.

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Administration and Enforcement

3. Administration and Enforcement1

T

his chapter addresses administration and enforcement issues, as well as general requirements for demonstrating compliance with the Code. The compliance requirements of the Code have been made lexible enough to allow architects and engineers the ability to comply with the Code and meet the speciic needs of their projects according to the climatic conditions of the site.

3.1 Compliance Requirements As mentioned in Chapter 2, all the buildings or building complexes with a connected load of 500 kW or greater or a contract demand of 600 kVA or greater have to comply with the Code. Buildings with 1,000 m2 or more of conditioned area are likely to fall under the above load conditions. The following sections which deal with mandatory and prescriptive requirements of new and existing buildings are related to this speciied threshold area. It is important to mention here that these mandatory and prescriptive requirements are applicable only where the building has a connected load of 500 kW or more or contract demand of 600kVA or more.

3.1.1

Mandatory Requirements

Compliance with the requirements of the Code shall be mandatory for all applicable buildings mentioned under Chapter 2 of the Code.

3.1.2

New Buildings

The Code compliance procedure requires the new building to fulill a set of mandatory provisions related to energy use as well as show compliance with the speciied requirements stipulated for the different building components and systems. The mandatory requirements are described in Sections 4.2, 5.2, 6.2, 7.2, and 8.2 of the Code. These mandatory provisions are discussed in the corresponding sections of this Guide. The Code also speciies prescriptive requirements for building components and systems. However, to maintain lexibility for the design and construction team, the Code compliance requirements can be met by following one of two methods: 1. Prescriptive Method speciies prescribed minimum energy eficiency parameters for various components and systems of the proposed building. The prescriptive requirements are covered in Chapter 4 through Chapter 8 dealing with the building envelope, HVAC systems, service hot water and pumping, lighting systems, and electric power respectively. To use the building envelope section as an example, designers can choose the prescriptive method that offers lexibility in selecting insulation for roof that meets speciied thermal characteristic (e.g. R-value, discussed in Chapter 4 of this Guide), in place of meeting prescriptive requirements of U-factor of the roof assembly. More explanation related to this method can be found in §3.2. 2. Whole Building Performance (WBP) is an alternative method to comply with the Code. This method is more complex than the Prescriptive Method, but offers considerable design lexibility. It allows for Code compliance to be achieved by optimizing the energy usage in various building components and systems (envelope, HVAC, lighting and other building systems) in order to ind the most cost-effective solution. WBP method requires an approved computer software program to model a Proposed Design, determine its annual energy use and compare it with the Standard Design of the building. Further explanation on the WBP Method can also be found in §3.2.

1

This Chapter has been adapted from ASHRAE User Manual (2004).

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Administration and Enforcement

Box 3-A provides an overview of the ECBC compliance process.

Box 3-A: Steps for meeting ECBC Compliance

3.1.3

Additions to Existing Buildings

Existing Building Compliance The Code also applies to additions in existing buildings. The requirements are triggered when new construction is proposed in the existing building. As per the Code: Where the addition plus the existing building exceeds the conditioned loor area of 1,000 m2 or more, the additions shall comply with the provisions of Chapter 4 through Chapter 8. Compliance may be demonstrated in either of the following ways: • The addition alone shall comply with the applicable requirements, or • The addition, together with the entire existing building, shall comply with the requirements of this Code that would apply to the entire building, as if it were a new building Exception to above: When space conditioning is provided by existing systems and equipment, the existing systems and equipment need not comply with this Code. However, any new equipment installed must comply with speciic requirements applicable to that equipment.

Example 3.1: ECBC Compliance for Additions to Existing Building An existing warehouse measures 120 m × 60 m. The warehouse is unconditioned, and the administrative ofice (30 m × 30 m) located in one corner. The ofice is served by a single-zone rooftop packaged HVAC system that provides both heating and cooling. The owner wants to expand the administrative ofice into the warehouse. The new ofice space will convert an area that measures 30 m × 15 m from unconditioned to conditioned space. The existing HVAC system has suficient capacity to serve the additional space. However, new ductwork and supply registers will need to be installed to serve the additional space.

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A: Area of Existing Ofice = 30m × 30m = 900m2 Additional Area of Ofice = 30m × 15m = 450m2 However, the Code applies to the 30m × 45m space that is being converted from unconditioned to conditioned space. The Code does not apply to the existing ofice or the existing warehouse space. The existing HVAC system does not need to be modiied, but the ductwork extensions must be insulated to the requirements of §5. The new lighting system installed in the ofice addition must meet the requirements of §7. The walls that separate the ofice addition from the unconditioned warehouse must be insulated to the requirements of §4. The exterior wall and roof are exterior building envelope components and must meet the Code requirements. Source: Adapted from ASHRAE User Manual (2004).

3.1.4

Alterations to Existing Buildings

When making alterations to an existing building, the portions of a building and its systems that are being altered must be made to comply with mandatory and prescriptive requirements. As per the Code: Where the existing building exceeds the conditioned loor area threshold (of 1000 m2 or more), portions of a building and its systems that are being altered shall meet the provisions of Chapter 4 through Chapter 8 (of the Code). The speciic requirements for alterations are described in the following subsections. Exception to above: When the entire building complies with all of the provisions of Chapter 4 through Chapter 8 (of the Code) as if it were a new building.

3.1.4.1 Building Envelope As per the Code: Alterations to the building envelope shall comply with the requirements of Chapter 4 (of the Code) or fenestration, insulation, and air leakage applicable to the portions of the buildings and its systems being altered. Exception to above: The following alterations need not comply with these requirements provided such alterations do not increase the energy usage of the building: • Replacement of glass in an existing sash and frame, provided the U-factor and SHGC of the replacement glazing are equal to or lower than the existing glazing • Modiications to roof/ceiling, wall, or loor cavities, which are insulated to full depth with insulation • Modiications to walls and loors without cavities and where no new cavities are created

3.1.4.2 Heating, Ventilation, and Air Conditioning As per the Code: Alterations to building heating, ventilating, and air-conditioning equipment or systems shall comply with the requirements of Chapter 5 (of the Code) applicable to the portions of the building and its systems being altered. Any new equipment or control devices installed in conjunction with the alteration shall comply with the speciic requirements applicable to that equipment or control device.

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3.1.4.3 Service Water Heating As per the Code: Alterations to building service water heating equipment or systems shall comply with the requirements of Chapter 6 applicable to the portions of the building and its systems being altered. Any new equipment or control devices installed in conjunction with the alteration shall comply with the speciic requirements applicable to that equipment or control device.

3.1.4.4 Lighting As per the Code: Alterations to building lighting equipment or systems shall comply with the requirements of Chapter 7 applicable to the portions of the building and its systems being altered. New lighting systems, including controls, installed in an existing building and any change of building area type as listed in Table 7.1 shall be considered an alteration. Any new equipment or control devices installed in conjunction with the alteration shall comply with the speciic requirements applicable to that equipment or control device. Exception to above: Alterations that replace less than 50% of the luminaires in a space need not comply with these requirements provided such alterations do not increase the connected lighting load.

3.1.4.5 Electric Power and Motors As per the Code: Alterations to building electric power systems and motors shall comply with the requirements of Chapter 8 applicable to the portions of the building and its systems being altered. Any new equipment or control devices installed in conjunction with the alteration shall comply with the speciic requirements applicable to that equipment or control device.

3.2 Compliance Approaches The Code requires that the building shall comply irst with all the mandatory provisions discussed in Chapter 4 to 8 (of the Code). But every building project is different: each building has its own site that presents unique opportunities and challenges, each building owner or user has different requirements, and climate and microclimate conditions can vary signiicantly among projects. Architects and engineers need lexibility in order to design buildings that address these diverse requirements. The Code provides this lexibility in a number of ways. Building components and systems have multiple options to comply with the Code requirements. To use the building envelope section as an example, designers can choose the Prescriptive Method that requires roof insulation be installed with a minimum R-value. Alternatively, the other options allow the designer to show compliance with the thermal performance (U-factor) of roof construction assembly. In addition building envelope tradeoff option discussed in Chapter 4 permits trade-offs among building envelope components (roof, walls, and fenestration) for Code compliance. If more lexibility is needed, the Whole Building Performance Method is available. a. Prescriptive Method The Code speciies a set of prescriptive requirements for building systems and components. Compliance with the Code can be achieved by meeting or exceeding the speciic levels described for each individual element of the building systems, covered in Chapter 4 through Chapter 8 of the Code. For building envelope, the Code provides a Trade-Off option that allows trading off the eficiency of one envelope element with another to achieve the overall eficiency level required by the Code. The envelope trade-off option is discussed in Chapter 12: Appendix D of ECBC.

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Administration and Enforcement

b. Whole Building Performance Method Use of energy simulation software is necessary to show ECBC compliance via the Whole Building Performance Method. Energy simulation is a computer-based analytical process that helps building owners and designers to evaluate the energy performance of a building and make it more energy-eficient by making necessary modiications in the design before the building is constructed. These computer-based energy simulation programs model the thermal, visual, ventilation, and other energyconsuming processes taking place within the building to predict its energy performance. The simulation program takes into account the building geometry and orientation, building materials, building façade design and characteristics, climate, indoor environmental conditions, occupant activities and schedules, HVAC and lighting system and other parameters to analyze and predict the energy performance of the building. Computer simulation of energy use can be accomplished with a variety of computer software tools and in many cases may be the best method for guiding a building project to be energy-eficient. However, this approach does require considerable knowledge of building simulation tools and very close communication between members of the design team. Appendix B of the Code describes the Whole Building Performance Method for complying with the Code. This method involves developing a computer model of the Proposed Design and comparing its energy consumption to the Standard Design for that building. Energy consumption in the Standard Design represents the upper limit of energy use allowed for that particular building under a scenario where all the prescriptive requirements of the Code are adopted. Code compliance will be achieved if the energy use in Proposed Design is no greater than the energy used in the Standard Design. Three basic steps are involved: 1. Design the building with energy eficiency measures; the prescriptive approach requirements provide a good starting point for the development of the design. 2. Demonstrate that the building complies with the mandatory measures (See sections 4.2, 5.2, 6.2, 7.2, and 8.2). 3. Using an approved simulation software, model the energy consumption of the building using the proposed features to create the Proposed Design. The model will also automatically calculate the energy use for the Proposed Design. If the energy use in Proposed Design is no greater than the energy use in the Standard Design, the building complies with the Code. Figure 3.1 shows a schematic depicting the WBP method

Figure 3.1: Design Process for the Whole Building Performance Method

The biggest advantage of using this approach is that it enables the design and construction team to make comparisons between different design options to identify the most cost-effective and energy-eficient design solution. For instance, the eficiency of the indoor lighting system might be improved in order to justify

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Administration and Enforcement

fenestration design that does not meet the prescriptive envelope requirements. As long as the total energy use of the Proposed Design does not exceed the allowed energy use in Standard Design, the building will be ECBC compliant. Note: For a detailed description of the computer simulation process and details, please refer to the ‘Energy Simulation Tip Sheet’ which can be accessed at: http://eco3.org/downloads/002-Implementationof ECBC/ Energy Simulation (Public Version).pdf

3.3 Administrative Requirements As per the Code: Administrative requirements relating to permit requirements, enforcement, interpretations, claims of exemption, approved calculation methods, and rights of appeal are speciied by the Authority Having Jurisdiction. Administration and enforcement of the Code is carried out by the local Authority Having Jurisdiction. This authority can be responsible for specifying permit requirements, code interpretations, approved calculation methods, worksheets, compliance forms, manufacturing literature, rights of appeal, and other data to demonstrate compliance. The Authority Having Jurisdiction will need to receive plans and speciications that show all pertinent data and features of the building, equipment, and systems. The process of designing code-compliant buildings will include different stages that begin with the design process, obtaining a building permit, completing the compliance submittals, the construction of the building followed by periodic inspections to make sure that construction is taking place per the requirement of the Code. Box 3-B discusses the Integrated Design Approach and Box 3-C provides guidelines for introducing the Code compliances and enforcement process. The process of complying with and enforcing the Code will require the involvement of many parties. Those involved may include the architect or building designer, building developer, contractor, engineers, energy consultant, owner, oficials doing compliance check, and third-party inspectors. Communication between these parties and an integrated design approach will be essential for the compliance/ enforcement process to run eficiently.

Box 3-B: Integrated Design Approach An integrated design approach brings together the various disciplines involved in designing a building and its systems and reviews their recommendations in a comprehensive manner. It recognizes that each discipline’s recommendations have an impact on other aspects of the building project. This approach allows for optimization of both building performance and cost. Often, the architect, mechanical engineer, electrical engineer, contractors, and other team members pursue their scope of work without adequate interaction with other team members. This can result in oversized systems or systems that are not optimized for eficient performance. For example, indoor lighting systems designed without consideration of day lighting opportunities or HVAC systems designed independently of lighting systems. An integrated design approach allows professionals working in various disciplines to take advantage of eficiencies that are not apparent when they are working in isolation. It can also point out areas where trade-offs can be implemented to enhance resource eficiency. The earlier that integration is introduced in the design process, the greater the beneit.

Box 3-C: The Compliance and Enforcement Process Although the compliance and enforcement process may vary somewhat with each adopting jurisdiction, the enforcement authority is generally the building department or other agency that has responsibility for approving and issuing building permits. When non-compliance or omissions are discovered during the plan review process, the building oficial may issue a correction list and require the plans and applications to be revised to bring them into compliance prior to issuing a building permit. In addition, the building oficial has the authority to stop work during construction when a code violation is discovered.

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Administration and Enforcement

The local building department has jurisdiction for determining the administrative requirements relating to permit applications. They are also the inal word on interpretations, claims of exemption, and rights of appeal. From time to time, the concerned authority will issue interpretations clarifying the intent of the Code. The local building department may take these under consideration, but the local building department still has the inal word. To achieve the greatest degree of compliance and to facilitate the enforcement process, the Code should be considered at each phase of the design and construction process (see Figure 3.2). 1. At the design phase, designers must understand both the requirements and the underlying intent of the Code. The technical sections of this Guide provide information that designers need to understand how the Code applies both to individual building systems and to the integrated building design. 2. At permit application, the design team must make sure that the construction documents submitted with the permit application contain all the information that the building oficial will need to verify that the building satisies the requirements of the Code. (This Guide provides compliance forms and worksheets to help ensure that all the required information is submitted.) 3. During plan review, the building oficial must verify that the proposed work satisies the requirements of the Code and that the plans (not just the forms) describe a building that complies with the Code. The building oficial may also make a list of items to be veriied later by the ield inspector. 4. During construction, the contractor must carefully follow the approved plans and speciications. The design professional should carefully check the speciications and working drawings that demonstrate compliance and should observe the construction in progress to see that compliance is achieved. The building oficial must verify that the building is constructed according to the plans and speciications. 5. After completion of construction, the contractor and/or designer should provide information to the building operators on maintenance and operation of the building and its equipment. Although only minimal completion and commissioning is required by the Code, most energy eficiency experts agree that full commissioning is important for proper building operation and management. Figure 3.2 maps the Design and Construction process along with the Compliances/Enforcement steps needed to show ECBC compliance.

Figure 3.2: The Building Design and Construction Process

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3.4 Compliance Documents 3.4.1

General

As per the Code: Plans and speciications shall show all pertinent data and features of the building, equipment, and systems in suficient detail to permit the Authority Having Jurisdiction to verify that the building complies with the requirements of this code. Details shall include, but are not limited to: Building Envelope: • Insulation materials and their R-values • Fenestration U-factors, SHGC, visible light transmittance (if using the trade-off approach), and air leakage • Overhang and sidein details • Envelope sealing details HVAC: • Type of systems and equipment, including their sizes, eficiencies, and controls • Economizer details • Variable speed drives • Piping insulation • Duct sealing • Insulation type and location • Report on HVAC balancing Service Hot Water and Pumping: • Solar water heating system details Lighting: • Schedules that show type, number, and wattage of lamps and ballasts • Automatic lighting shutoff details • Occupancy sensors and other lighting control details • Lamp eficacy for exterior lamps Electrical Power: • Schedules that show transformer losses, motor eficiencies, and power factor correction devices • Electric check metering and monitoring system details The documents submitted should include suficient detail to allow thorough review by the Authority Having Jurisdiction for Code compliance. Additional information may be requested by the authority, if needed, to verify compliance. The compliance forms and worksheets are provided with this Guide (Appendix G) and are intended to facilitate the process of complying with the Code. These forms serve a number of functions: • They provide a permit applicant and designer the information that needs to be included on the drawing. • They provide a structure and order for the necessary calculations. The forms allow information to be presented in a consistent manner, which is a beneit to both the permit applicant and the enforcement agency.

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Administration and Enforcement

• They provide a roadmap showing the enforcement agency where to look for the necessary information on the plans and speciications. • They provide a checklist for the enforcement agency to help structure the drawing check process. • They promote communication between the drawings examiner and the ield inspector. • They provide a checklist for the inspector.

3.4.2

Supplemental Information

As per the Code: The Authority Having Jurisdiction may require supplemental information necessary to verify compliance with this Code, such as calculations, worksheets, compliance forms, manufacturer’s literature, or other data.

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Building Envelope

4. Building Envelope 4.1 General Overview

he building envelope refers to the exterior façade, and is comprised of opaque components and T fenestration systems. Opaque components include walls, roofs, slabs on grade (in touch with ground), basement walls, and opaque doors. Fenestration systems include windows, skylights, ventilators, and doors that are more than one-half glazed. The envelope protects the building’s interior and occupants from the weather conditions and shields them from other external factors e.g. noise, air pollution, etc.

The building envelope depicted here by the green line, which separates the conditioned space from the unconditioned space.

Figure 4.1: Building Envelope Envelope design strongly affects the visual and thermal comfort of the occupants, as well as energy consumption in the building. Box 4-A discusses the there modes of heat transfer (Conduction, Convection and Radiation) in the building.

Box 4-A: How Heat Transfer Takes Place in a Building Heat transfer takes place through walls, windows, and roofs in buildings from higher temperature to lower temperature in three ways-conduction, convection, and radiation. Conduction is the transfer of heat by direct contact of particles of matter within a material or materials in physical contact. Convection is the transfer of heat by the movement of a luid (air or gas or liquid). Radiation is the movement of energy/heat through space without relying on conduction through the air or by the movement of air. The surface of the sun, estimated to be at a temperature of about 5500°C, emits electromagnetic waves. These waves are also known as solar radiation or short-wave radiation with wave length in the range of 0.3 to 2.5 microns or 300 nm to 2500 nm, and has three components: Ultra Violet (UV), Visible (the sun light which is visible to human eye) and “Solar (or Near) Infrared” as depicted in the igure Figure 4.2:

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Figure 4.2: The Solar and Blackbody Spectrum When the ‘Solar Infrared’ component of the waves comes in contact with the earth or any object or a building, it transfers its energy to the object/building in the form of heat. The phenomenon is known as solar radiation heat transfer. Radiation heat transfer, in fact, can be between any two bodies having different temperatures with heat transfer taking place from the body at higher temperature to the body at the lower temperature. The Figure 4.3 shows all three modes of heat transfer across a building wall facing the external environment.

Figure 4.3: Schematic Showing Three Modes of Heat Transfer Conductive heat transfer across the envelope also depends upon the conductivity of the building material used. Different materials offer different thermal resistance to the conduction process. Individually, walls and roofs are comprised of a number of layers composed of different building materials. Thus, it is important to establish overall thermal resistance and heat transfer coeficient (U-factor), also termed thermal transmittance. The concepts of thermal resistance and U- factor are discussed in Box 4-B for better understanding.

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Box 4-B: Conduction and Resistance Conduction Conduction is heat transfer through a solid medium as a result of a temperature gradient. The heat low direction is, in accordance with the second law of thermodynamics, from a region of higher temperature to that of lower temperature. The Conductivity is the property of material. The rate of heat transfer (q) through a homogeneous medium is given by Fourier’s Law of Conduction: dT q = kA dx 6 W @ q : Rate of heat transfer [W] k A T x

: Thermal conductivity of the material [Wm2·K-1] : Area [m2] : Temperature [K] : Distance in the direction of heat low [m]

Resistance Thermal Resistance is proportional to the thickness of material of construction and inversely proportional to its conductivity. This, a lower value of conductivity means less heat low and so does the greater thickness of material. Together these parameters form the ‘Thermal Resistance’ to the process of heat conduction. d R = k 6 m2 ·K· W- 1 @ Description of Surface Resistance The total thermal resistance RT of a plane element consisting of thermally homogeneous layers perpendicular to the heat low is calculated by the following formula: RT : Rsi + Rt + Rse Where Rt is the thermal resistances of the component in the wall/roof. Rt : R1 + R2+ …+ Rn For the calculation of the thermal transmittance under ordinary building conditions, the seasonal mean values of the exterior surface thermal resistance (Rse) and the interior surface thermal resistance (Rsi) can be obtained from Table 4.1. These values are the result of empirical studies and merely represent magnitudes of order. They consider both convection and radiation inluences. Table 4.1: Values of Surface Film Resistance Based on Direction of Heat Flow Rsi Direction of Heat Flow Horizontal Up 0.13

0.10

Rse Down 0.17

Direction of Heat Flow Horizontal Up 0.04

0.04

Down 0.04

Thermal Resistance of an Element Consisting of Homogenous Layers A building element is usually composed of a number of different materials. When materials are placed in series, their thermal resistances are added so that the same area will conduct less energy for a given temperature difference. Formation of air ilm at the surface of wall or roof, due to convection movements of air, also provides resistance to the heat low, similar to the construction material. The total resistance of the wall or roof includes all of the resistances of the individual materials that make it up as well as both the internal and external air-ilm resistance. R1, R2, …, Rn are the thermal resistance of each layer. 1 Thermal Resistance is also depicted as reciprocal of Thermal Conductance (U): R = U

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Thermal Resistance of Unventilated Air Layers Table 4.2 gives the thermal resistances of unventilated air layers (valid for emittance of the bounding surfaces > 0.8). The values under "horizontal" should be used for heat low directions ± 30° from the horizontal plane; for other heat low directions, the values under "up" or "down" should be used. Table 4.2: Thermal Resistances of Unventilated Air Layers Between Surfaces with High Emittance Thermal Resistance (m2·K·W-1) Direction of Heat Flow

Thickness of Air Layer (mm) Horizontal

Up

Down

5

0.12

0.10

0.10

7

0.12

0.12

0.12

10

0.14

0.14

0.14

15

0.16

0.16

0.16

25

0.18

0.17

0.18

50

0.18

0.17

0.20

100

0.18

0.17

0.20

300

0.18

0.17

0.21

Example 4.1: R -Value Calculations for Cavity Wall Construction

Figure 4.4: Typical Cavity Wall Construction R1: Resistance for Layer 1 (13 mm Gypsum Plaster) = 0.056 K·m2/W (from ECBC Table 11.4) R2: Resistance of Layer 2 (230 mm brick wall, density=1920kg/m3) = d2/k2 = 0.230/0.81 =0.284 K·m2/W R3: Resistance of Layer 3 (115 mm air gap)

(from ECBC Table 11.4) =1.8 Km2/W (from Table 4.1)

R4: Resistance of Layer 4 (115 mm brick wall, density=1920kg/m3) = d4/k4 = 0.115/0.81 =0.1426 K·m2/W (from ECBC Table 11.4) Rt: Minimum R-value for the composite wall

= R1+ R2+ R3 + R4 = 0.056+ 0.2840 + 0.18 + 0.1426 = 0.6626 K·m2/W

RT: Rsi+ Rt+R se

= 0.1+ 0.6626 +0.04= 0.8026

Maximum U-factor for the composite wall: Umin

= 1/RT = 1/0.8026 = 1.246 W/m2·K

The design of the building envelope is generally the responsibility of an architect. The building designer is responsible for making sure that the building envelope is energy-eficient and complies with the mandatory Energy Conservation Building Code (ECBC) User Guide

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Building Envelope

and prescriptive requirements of the Code. It also provides ‘trade-off options’ which allows lexibility to the designer to ‘trade-off ’ prescriptive requirements of building components, while meeting the minimum energy performance requirements of the envelope.

4.2 Mandatory Requirements 4.2.1

Fenestration

Heat transfer across glazing products or fenestration (windows, door, and skylights) is similar to the heat transfer that takes place across walls and roofs through conduction and convection. So, U-factor of glazing is analogous to the U-factor of wall assembly. In addition, direct solar radiation contributes to the solar heat gain through the fenestration system. Box 4-C discusses the concept of Solar Heat Gain Coeficient (SHGC). Fenestration and doors must be rated using procedures and methods speciied in the ECBC. Three fenestration performance characteristics are signiicant in the ECBC: U-factor, SHGC, and Visible Light Transmittance (VLT). These are reviewed below: The U-factor of fenestration is very important to the energy eficiency of buildings, especially in cold climates. The U-factor must account for the entire fenestration product, including the effects of the frame, the spacers in double glazed assemblies, and the glazing. There are a wide variety of materials, systems, and techniques used to manufacture fenestration products, and accurately accounting for these factors is of utmost importance when calculating the U-factor. According to ECBC, Fenestration U-factors must be determined in accordance with ISO-15099.

Box 4-C: Solar Heat Gain Coeicient and U-Factor Conduction heat low through the fenestration (e.g. glass windows) is similar to the process discussed for walls and roofs. However regardless of outside temperature, heat gain through the fenestration is also dependent on direct and indirect solar radiation. The ability to control this heat gain is characterized in terms of SHGC. SHGC is the ratio of the solar heat gain that passes through the fenestration to the total incident solar radiation that falls on the fenestration. The solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then re-radiated, convected, or conducted into the interior space. SHGC indicates how well the glazing/glass and fenestration products insulate heat caused by sun falling directly on the glass.

Figure 4.5: Direct and Indirect Solar Radiation In hot climates, SHGC is more important than the U-factor of the glazing. A lower SHGC means that lesser heat can pass through the glazing. The SHGC is based on the properties of the glazing material, whether the window has single, double, or triple glazing, and the window operation (either operable or ixed). Glazing units with a low SHGC will help reduce the air conditioning energy use during the cooling season.

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Figure 4.6: Heat Transfer (Conduction, Convection, & Radiation) and Iniltration Across a Window

4.2.1.1 U-factors Clear glass, which is the most common type of glass used today, has no signiicant thermal resistance (R-value) from the pane itself. It has a value of R-0.9 to R-1.0 due to the thin ilms of air on the interior and exterior surfaces of the glass. The U-factor (thermal conductance), must account for the entire fenestration system including the effects of the frame, the spacers in double glazed assemblies, and the glazing. There are a wide variety of materials, systems, and techniques used to manufacture fenestration products, and accurately accounting for these factors is of utmost importance when meeting the fenestration requirements. The Code also speciies U-factor for sloped glazing and skylights, and minimum U-factors for unrated products. ECBC has used W/m2·C as the unit for U-factor. Since differences in temperature are always denoted in K in physics literature, ECBC User Guide has used W/m2·K as the unit of U-factor. Wherever, °C was being used for differences in temperature, it has been replaced with K in the Guide. U-factors for fenestration systems (including the sash and frame) are required to be determined in accordance with ISO-15099 (as speciied in ECBC §11: Appendix C) by an accredited independently laboratory and labeled and certiied by the manufacturer or other responsible party. Box 4-D briely explains how these issues are addressed in US.

Box 4-D: How Fenestration Products are Tested, Certiied, and Labeled in the U.S. In the U.S, the fenestration U-factors are determined in accordance with the National Fenestration Rating Council (NFRC) Standard 100. NFRC is a membership organization of window manufacturers, researchers, and others that develops, supports, and maintains fenestration rating and labeling procedures. Most fenestration manufacturers have their products rated and labeled through the NFRC program. Certiied products receive an 8 ½ by 11 inch NFRC label that lists the U-factor, SHGC, and the visible transmittance.

4.2.1.2 Solar Heat Gain Coeicient The ECBC requires that SHGC be determined in accordance with ISO-15099 by an accredited independent laboratory, and labeled and certiied by the manufacturer or other responsible party. SHGC has replaced Shading Coeficient (SC) as the preferred speciication for solar heat gain through fenestration products. Designers should insist on getting SHGC data from the manufacturers. However, it should be kept in mind that only SHGC data that is certiied by an accredited independent testing laboratory can be used to show ECBC compliance.

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4.2.1.3 Air Leakage Air leakage for glazed swinging entrance doors and revolving doors shall not exceed 5.0 l/s·m2. Air leakage for other fenestration and doors shall not exceed 2.0 l/s·m2. The irst set of air leakage requirements deals with inadvertent leaks at joints in the building envelope. In particular, the standard states that exterior joints, cracks, and holes in the building envelope shall be caulked, gasketed, weather stripped, or otherwise sealed. The construction drawings should specify sealing, but special attention is needed in the construction administration phase to assur e proper workmanship. A tightly constructed building envelope is largely achieved through careful construction practices and attention to detail. Poorly sealed buildings can cause problems for maintaining comfort conditions when additional iniltration loads exceed the HVAC design assumptions. This can be a signiicant problem in high-rise buildings due to stack effect and exposure to stronger winds.

4.2.2

Opaque Construction

U-factors shall be determined from the default tables in Appendix C §11 or determined from data or procedures contained in the ASHRAE Fundamentals, 2005.

4.2.3

Building Envelope Sealing

Air leakage can also occur through opaque construction. Apart from adding cooling or heating load in the building, air leakage can cause condensation within walls and roof can damage insulation material and degrade other building materials. Box 4-E discusses these aspects in more detail. It must be noted that building sealing is more important in air-conditioned buildings. In naturally ventilated buildings, the concept of building ceiling and tight envelope runs counter to conventional and traditional wisdom.

Box 4-E: Building Envelope Sealing and Air Leakage Air leakage is the passage of air through a building envelope, wall, window, joint, etc. Leakage to the interior is referred to as iniltration and leakage to the exterior is referred to as ex-iltration. Excessive air movement signiicantly reduces the thermal integrity and performance of the envelope and is, therefore, a major contributor to energy consumption in a building. A tightly constructed building envelope is largely achieved through careful construction practices and attention to detail. Building envelopes should be carefully designed to limit the uncontrolled entry of outdoor air into the building. Air leakage introduces sensible heat into conditioned spaces. In climates with moist outdoor conditions, it is also a major source of latent heat. Latent heat must be removed by the air-conditioning system at considerable expense. In addition to causing energy loss, excessive air leakage can cause condensation to form within and on walls. This can create many problems including reducing insulation R-value, permanently damaging insulation, and seriously degrading materials. It can rot wood, corrode metals, stain brick or concrete surfaces, and in extreme cases cause concrete to break, bricks to separate, mortar to crumble and sections of a wall to fall jeopardizing the safety of occupants. It can corrode structural steel, re-bar, and metal hangars and bolts with very serious safety and maintenance consequences. Moisture accumulation in building materials can lead to the formation of mold that may require extensive remedying the situation. Virtually anywhere in the building envelope where there is a joint, junction or opening, there is potential for air leakage. Air leakage will cause the HVAC system to run more often and longer at one time, and still leave the building uncomfortable for its occupants. All openings in the building envelope, including joints and other openings that are potential sources of air leakage, should be to be sealed to minimize air leakage. It means that all gaps between wall panels, around doors, and other construction joints must be well sealed. Ceiling joints, lighting ixtures, plumbing openings, doors, and windows should all be considered as potential sources of unnecessary energy loss due to air iniltration. ECBC identiies several areas in the building envelope where attention should be paid to iniltration control. These include:

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a. Joints around fenestration and doorframes. b. Openings at penetrations of utility services through roofs, walls, and loors. c. Site-built fenestration and doors. d. Building assemblies used as ducts or plenums. e. Joints, seams, and penetrations of vapor retarders. f. All other openings in the building envelope. It is also recommended that junctions between walls and foundations, between walls at building corners, between walls and structural loors or roofs, and between walls and roof or wall panels. Fenestration products, including doors, can also signiicantly contribute to iniltration. Although not included in the Code, it is recommended that fenestration products should have iniltration less than 0.4 cfm/ft² (2.0 l/s·m²). For glazed entrance doors that open with a swinging mechanism and for revolving doors, it is recommended that iniltration be limited to 1.0 cfm/ft² (5.0 l/s·m²).

4.3 Prescriptive Requirements For envelope component-based compliance approach, ECBC sets requirements for: • • • • •

4.3.1

Exterior roofs and ceilings Cool roofs Opaque walls Vertical fenestration Skylights

Roofs

In roofs, the U-factor for the overall assemblies or minimum R-values for the insulation must be complied with the provisions of the Code. ECBC Appendix C provides values for typical constructions. In real practice, the heat gains through the walls, roof, and fenestration depends upon the climate zone in which the building is located. The National Building Code of India, 2005 has divided the country in ive climate zones (Hot-Dry; Warm-Humid; Composite; Temperate/Moderate; and Cold), and the air temperature and humidity variations that exist need to be considered while designing the building envelope.

Box 4-F: Role of Climate Zone The ECBC building envelope requirements are based on the climate zone in which the building is located. ECBC deines ive climate zones (hot-dry; warm-humid; composite; temperate; cold), which are distinctly unique in their weather proiles. Appendix E of the Guide provides additional information on the ive climatic zones. Based on the characteristics of climate, the thermal comfort requirements in buildings and their physical manifestation in architectural form are also different for each climate zone (See Table 4.3). These physical manifestations, in turn, dictates the ECBC requirements for the envelope, as well as other building components that are applicable to the building. Table 4.3: Comfort Requirements and Physical Manifestations in Buildings HOT AND DRY CLIMATE ZONE Thermal Requirements

Physical Manifestation

Reduce Heat Gain Decrease exposed surface area

Orientation and shape of building

Increase thermal resistance

Insulation of building envelope

Increase thermal capacity (Time lag)

Massive structure

Increase buffer spaces

Air locks/lobbies/balconies/verandahs

Decrease air exchange rate (ventilation during day-time)

Smaller windows openings, night ventilation

Increase shading

External surfaces protected by overhangs, ins and trees

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Increase surface relectivity

Pale colour, glazed china mosaic tiles etc.

Reduce solar heat gain

Use glazing with lower SHGC and provide shading for windows. Minimize glazing in East and West

Promote Heat Loss Increase air exchange rate (Ventilation during night-time)

Courtyards/wind towers/arrangement of openings

Increase humidity levels

Trees, water ponds, evaporative cooling

WARM AND HUMID CLIMATE ZONE Thermal Requirements

Physical Manifestation

Reduce Heat Gain Decrease exposed surface area

Orientation and shape of building

Increase thermal resistance

Roof insulation and wall insulation Relective surface of roof

Increase buffer spaces

Balconies and verandas

Increase shading

Walls, glass surfaces protected by overhangs, ins and trees

Increase surface relectivity

Pale color, glazed china mosaic tiles, etc.

Reduce solar heat gain

Use glazing with lower SHGC and provide shading for windows. Minimize glazing in East and West

Promote Heat Loss Increase air exchange rate (Ventilation throughout the day)

Ventilated roof construction. Courtyards, wind towers and arrangement of openings

Decrease humidity levels

Dehumidiiers/desiccant cooling

Thermal Requirements

MODERATE CLIMATE ZONE Physical Manifestation

Reduce Heat Gain Decrease exposed surface area

Orientation and shape of building

Increase thermal resistance

Roof insulation and east and west wall insulation

Increase shading

East and west walls, glass surfaces protected by overhangs, ins and trees

Increase surface relectivity

Pale colour, glazed china mosaic tiles, etc.

Promote Heat Loss Increase air exchange rate (Ventilation)

Courtyards and arrangement of openings

COLD (Cloudy/Sunny) CLIMATE ZONE Thermal Requirements

Physical Manifestation

Reduce Heat Loss Decrease exposed surface area

Orientation and shape of building. Use of trees as wind barriers

Increase thermal resistance

Roof insulation, wall insulation and double glazing

Increase thermal capacity (Time lag)

Thicker walls

Increase buffer spaces

Air locks/Lobbies

Decrease air exchange rate

Weather stripping and reducing air leakage

Increase surface absorptive

Darker colours

Promote Heat Gain Reduce shading

Walls and glass surfaces

Trapping heat

Sun spaces/green houses/Trombe walls etc.

COMPOSITE CLIMATE ZONE Thermal Requirements

Physical Manifestation

Reduce Heat Gain in Summer and Reduce Heat Loss in Winter Decrease exposed surface area

Orientation and shape of building. Use of trees as wind barriers

Increase thermal resistance

Roof insulation and wall insulation

Increase thermal capacity (Time lag)

Thicker walls

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Increase buffer spaces

Air locks/Balconies

Decrease air exchange rate

Weather stripping

Increase shading

Walls, glass surfaces protected by overhangs, ins and trees

Increase surface relectivity

Pale color, glazed china mosaic tiles, etc.

Reduce solar heat gain

Use glazing with lower SHGC and provide shading for windows. Minimize glazing in East and West

Promote Heat Loss in Summer/Monsoon Increase air exchange rate (Ventilation)

Courtyards/wind towers/arrangement of openings

Increase humidity levels in dry summer

Trees and water ponds for evaporative cooling

Decrease humidity in monsoon

Dehumidiiers/desiccant cooling

Source: Nayak and Prajapati (2006). Handbook on Energy Conscious Buildings

Exterior roofs can meet the prescriptive requirements in one of two ways: • Use the required R-value of the insulation (this R-value does not apply to building materials or air ilm. It should be referred exclusively for insulation), or • Use a roof assembly U-factor that meets the maximum U-factor criterion for thermal performance (see ECBC Table 4.3.1). The U-factor takes into account all elements or layers in the construction assembly, including the sheathing, interior inishes, and air gaps, as well as exterior and interior air ilms. As per the Code: The roof insulation shall not be located on a suspended ceiling with removable ceiling panels. The Code requirements for the U-factor and R-values for 24 hours use buildings and daytime use buildings for ive climate zones as shown in Table 4.4 below. Table 4.4: Roof Assembly U-Factor and Insulation R-value Requirements (ECBC Table 4.3.1) Climate Zone

24-Hour use buildings Hospitals, Hotels, Call Centers etc. Maximum U-factor of the overall assembly (W/m2·K)

Composite Hot and Dry Warm and Humid Moderate Cold

Daytime use buildings Other Building Types

Minimum R-value Maximum U-factor of of insulation alone the overall assembly (m2·K/W) (W/m2·K)

Minimum R-value of insulation alone (m2·K/W)

U-0.261

R-3.5

U-0.409

R-2.1

U-0.261

R-3.5

U-0.409

R-2.1

U-0.261

R-3.5

U-0.409

R-2.1

U-0.409

R-2.1

U-0.409

R-2.1

U-0.261

R-3.5

U-0.409

R-2.1

Some recommended practices for proper installation and protection of insulation are provided below: Insulation

The irst set of mandatory requirements addresses the proper installation and protection of insulation materials. It is recommended that insulation materials be installed according to the manufacturer’s recommendations and in a manner that will achieve the rated insulation R-value. Compressing the insulation reduces the effective R-value and the thermal performance of the construction assembly. Substantial Contact

It is recommended that insulation be installed in a permanent manner and in substantial contact with the inside surface of the construction assembly. If the insulation does not entirely ill the cavity, the air gap should be on the outside surface. Maintaining substantial contact is particularly important (and problematic) for batt insulation installed between loor joists. Without proper support, gravity will cause the insulation to fall away from the loor surface, leaving an air gap above the insulation. Air currents will ultimately ind their way to the gap, and when they do, the effectiveness of the insulation will be substantially reduced.

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Insulation Above Suspended Ceilings

It is not good practice to install insulation directly over suspended ceilings with removable ceiling panels. This is because the insulation’s continuity is likely to be disturbed by maintenance workers. Also, suspended ceilings may not meet the ECBC’s iniltration requirements unless they are properly sealed. Compliance with this requirement could have a signiicant impact in some parts of the country, as it is common practice to install insulation over suspended ceilings. Many building codes will consider the space above the ceiling to be an attic and require that it be ventilated to the exterior. If vented to the exterior, air in the attic could be quite cold (or hot) and the impact of the leaky suspended ceiling would be made worse. Insulation Protection

It is strongly recommended that insulation be protected from sunlight, moisture, landscaping equipment, wind, and other physical damage. Rigid insulation used at the slab perimeter of the building should be covered to prevent damage from gardening or landscaping equipment. Rigid insulation used on the exterior of walls and roofs should be protected by a permanent waterproof membrane or exterior inish. In general, a prudent designer should pay attention to moisture migration in all building construction. Vapor retarders prevent moisture from condensing within walls, roofs, or loors but care should be taken to install them on the correct side (warmer or cooler side) of the walls and roofs to prevent water damage. Water condensation can damage the building structure and can seriously degrade the performance of building insulation and create many other problems such as mold and mildew. The designer should evaluate the thermal and moisture conditions that might contribute to condensation and make sure that vapor retarders are correctly installed to prevent condensation. In addition to correctly installing a vapor retarder, it is important to provide adequate ventilation of spaces where moisture can build up. Figure 4.7 shows some common techniques to insulate different types of rooing systems.

Pre-Fabricated Metal Roofs Showing Thermal Blocking of Purlins

Steel Joist Roof with Insulated Cavities

Metal Framed Ceiling Insulation

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Insulation entirely above deck: Insulation is installed above (a) concrete, (b) wood or (c) metal deck in a continuous manner. (a), (b), and (c) are shown sequentially right to left.

Steel Joist Roof with Continuous Insulation

Figure 4.7: Building Roofs

A. RCC Slab Insulated with Vermiculite B. RCC Slab Insulated with Earthen Pots

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C. RCC Slab Insulated using Foamular Metric

Figure 4.8: Typical Insulation Techniques for RCC Roof Construction

4.3.2

Cool Roofs

Depending on the material and construction, a roof will have different properties that determine how it conducts heat to the inside of the building. “Cool roofs” are roofs covered with a relective coating that has a high emissivity property that is very effective in relecting the sun’s energy away from the roof surface. These “cool roofs” are known to stay 10°C to 16°C cooler than a normal roof under a hot summer sun; this quality greatly reduces heat gain inside the building and the cooling load that needs to be met by the HVAC system. Box 4-G discusses how solar heat radiation is relected, absorbed and emitted from the roof and how these concepts are used in developing cool roofs.

Box 4-G: Relectance, Absorptance, and Emissivity The heat transfer process involved in the roof, is similar to the heat transfer that takes in a wall. Heat transfer across the roof is more prominent compared to the wall because of higher incidence of solar radiation. Depending on the properties of the roof material and construction, the roof relects part of the solar radiation back to the environment, and absorbs the other part of the heat in the roof (See Figure 4.9). Finally, portion of the absorbed heat in the roof is emitted as long-wave radiation back to the environment and the remaining part of the absorbed heat is conducted inside of the building. This heat transfer process is governed by the Solar Relectance and Emissivity (Thermal Emittance) properties of the roof material, apart from the thermal conductivity of the materials used in the roof.

Figure 4.9: Heat Transfer Through Roof

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Solar Relectance and Absorptance The solar relectance is the fraction of solar radiation relected by roof. The complement of relectance is absorptance; whatever radiant energy incident on a surface that is not relected is absorbed in the roof. The relectance and absorptance of building materials are usually measured across the solar spectrum, since these are exposed to that range of wavelength. Relectance is measured on a scale of 0 to 1, with 0 being a perfect absorber and 1 being a perfect relector. Absorptance is also rated from 0 to 1, and can be calculated from the relation: Relectance + Absorptance = 1. Emissivity or Thermal Emittance Emissivity (or thermal emittance) of a material (usually written ε or e) is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. It is a measure of a material’s ability to radiate the absorbed energy. A true black body would have an e =1 while any real object would have e 0.1)

Glazing complies with ECBC

4.3.5

= 0.09 (EA < 0.1)

Glazing does not comply with ECBC

Skylights

A skylight is a fenestration surface having a slope of less than 60 degrees from the horizontal plane. Other fenestration, even if mounted on the roof of a building, is considered vertical fenestration. Skylights can be installed into a roof system either lush-mounted or curb-mounted (including site built). In order to create a positive water low around them, skylights are often mounted on “curbs” set above the roof plane. However, these curbs, rising 6 to 12 inches (15 to 30 centimeters) above the roof, create additional heat loss surfaces right where the warmest air of the building tends to collect. Portions of roof that serve as curbs that mount the skylight above the level of the roof (See below) are part of the opaque building envelope.

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Figure 4.12: Skylight Installations As per the Code: Skylights shall comply with the maximum U-factor and maximum SHGC requirements of Table 4.6. Skylight area is limited to a maximum of 5% of the gross roof area for the prescriptive requirement. Table 4.10: Skylight U-Factor and SHGC Requirements (ECBC Table 4.6) Maximum U-factor Climate

Maximum SHGC

With Curb

w/o Curb

0-2% SRR

2.1-5% SRR

Composite

11.24

7.71

0.40

0.25

Hot and Dry

11.24

7.71

0.40

0.25

Warm and Humid

11.24

7.71

0.40

0.25

Moderate

11.24

7.71

0.61

0.4

Cold

11.24

7.71

0.61

0.4

SRR: Skylight roof ratio which is the ratio of the total skylight area of the roof, measured to the outside of

the frame, to the gross exterior roof. See §11.2.2 for typical complying skylight constructions.

Example 4.3: Prescriptive Requirements for Skylights Location

: Chennai

Climate Zone Building Type Roof Area

: Warm-Humid : Daytime Use Building : 1,863 m2

Roof Insulation Wall Area

: Rigid Board 1 inch R= 2.1 m2·°K/W : 3,706 m2

Wall Insulation Fenestration Area

: Rigid Board 1 inch R= 1.41 m2·°K/W : 487 m2

Window to Wall ratio : 487/3706 = 13% SHGC : 0.20 U–factor

: 3.30

Skylight Area : 112 m2 Skylight to Roof Area : 112/1863= 6% Q: Does my building envelope comply with the ECBC using the prescriptive path? A: No, this building does not comply because the prescriptive approach limits skylights area to a maximum of 5% of the roof area. This building would need to comply under the envelope trade off option of the Whole Building Approach. As with windows, the skylight-roof ratio must be calculated separately for each space category. The criteria for each space category are determined from its own skylight-roof ratio, not the skylight-roof ratio for the whole building.

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Box 4-K: Glazing Selection for ECBC Compliance What is the most important feature that a building professional should look for regarding windows, doors, and skylights? The SHGC and U-factor ratings are the most important items to verify during inspections. Building professionals should verify that the ratings of the installed windows, doors, and skylights meet or exceed the ratings speciied on the plans. It is also important to verify that the same window area has been installed as the area shown on the plans and that the glass orientation on the plans and building are consistent. What is Solar Heat Gain Coeficient? The Solar Heat Gain Coeficient is a measure of the percentage of heat from the sun that gets through a window or other fenestration product. The SHGC is expressed as a number between 0 and 1. The lower a window’s SHGC, the less solar heat it transmits to the interior of the building. SHGC can also refer to shading so the lower the SHGC the more effective the product is at shading the heat gain from entering the interior. What is low-e glass? Low-e stands for low-emissivity and refers to a special coating that reduces the heat transfer of a window assembly. Low-e coated products that reduce solar heat gain can be produced by adding a metallic coating either while the glass is in a molten state or by applying to the glass after it has cooled to a solid state. Low-e glass is readily available from all the glass and window manufacturers. The coatings typically add about 10% to the cost of a window but costs vary by product type, by manufacturer, by retailer and by location. What is spectrally selective glass? The sun emits visible solar radiation in the form of light and infrared radiation that cannot be seen, but causes heat. Spectrally selective glass transmits a high proportion of the visible solar radiation, but screens out radiant heat from the sun – signiicantly reducing the need to cool a building’s interior. Spectrally selective glass is used to describe low-e coated glass that lowers the SHGC. How can I be sure I have spectrally selective glass? The SHGC rating for the product is the key to determining whether you have glass with a spectrally selective coating. In general, windows with a spectrally selective low-e coating will have SHGC ratings of 0.40 or lower.

4.4 Building Envelope Trade-Of Option This is a systems-based approach, where the thermal performance of individual envelope components can be reduced if compensated by higher eficiency in other building components (i.e., using higher wall insulation could allow for a less stringent U-factor requirement for windows, or vice versa.) These trade-offs typically occur within major building systems – roofs, walls, fenestration, overhangs etc. This method offers the designer more lexibility than strictly following the prescribed values for individual elements. The thermal performance of one envelope component such as the roof can fail to meet the prescriptive requirements as long as other components perform better than what is required. Trade-offs are permitted only between building envelope components. It is not possible, for instance, to make trade-offs against improvements in the lighting or HVAC systems. However, this makes using the envelope trade-off option more complicated than the prescriptive method. It is necessary to calculate the surface area of each exterior and semiexterior surface; all areas must also be calculated separately for each orientation. The equations used for calculating envelope performance factor under envelope trade-offs are documented in ECBC §12 Appendix D.

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5. Heating, Ventilation and Air Conditioning 5.1 General

H

eating, Ventilation and Air Conditioning (HVAC) refers to the equipment, distribution systems, and terminals that provide, either collectively or individually, the heating, ventilation, or air-conditioning requirement to a building or a portion of building. The HVAC system accounts for a signiicant portion of a commercial building’s energy use. HVAC energy use in a commercial building can increase/decrease signiicantly depending on how eficiently the combination of air side systems and central plant operates. Proven technologies and design concepts can be used to build energy eficiencies in the system and generate signiicant energy and cost savings. HVAC systems also affect the health, comfort, and productivity of occupants. Issues like user discomfort, improper ventilation, lack of air movement and poor indoor air quality, and poor acoustic design are linked to HVAC system design and operation and can be improved. In many existing buildings, envelope upgrades are often necessary to improve comfort and energy eficiency, through improvements such as reducing envelope leakage. Generally, upgrading an existing building envelope is expensive. Other strategies such as central plant, airside or control system upgrade may be necessary to improve occupant comfort and energy eficiency. The best HVAC design considers all the interrelated building systems while addressing indoor air quality, thermal comfort, energy consumption, and environmental beneits. Optimizing both the design and the beneits requires that the architect and mechanical system designer address these issues early in the schematic design phase and continually revise subsequent decisions throughout the remaining design process. It is also essential that a process be implemented to monitor proper installation and operation of the HVAC system throughout construction. An effective commissioning plan for each of the systems at full load and part load including controls calibration and commissioning is essential to the optimal performance of the building. General concepts of HVAC systems are discussed in more details in Box 5-A and Box 5-B.

Box 5-A: Air Conditioning System Basics Basic components of the system include a compressor, condenser (air-cooled or water cooled), evaporator and an expansion device., similar to that of a domestic refrigerator. C Discharge Line Condenser

Liquid Line

B

Expansion Device

Compressor

A Suction Line

D Evaporater

Room air is drawn across an indoor coil called the evaporator that cools and dehumidiies the air during the cooling cycle. The condenser condenses the refrigerant and transforms the high pressure vapor into high pressure liquid. Heat is rejected via air drawn across the condenser coils using fans (air-cooled condenser) or using a shell and tube heat exchanger in conjunction with a condenser water reticulation system and cooling towers (water cooled condenser). The expansion device transforms the high pressure high temperature liquid refrigerant to low pressure low temperature mixture of refrigerant liquid and vapor. This mixture fully evaporates in the evaporator absorbing the heat from the water (cooling the water in a chilled water system) or cooling the air drawn across the coil (direct expansion system). The compressor then raises the pressure and temperature of the refrigerant and the cycle continues on.

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Box 5-B: Heating Systems Heating system types can be classiied fairly well by the heating equipment type. The heating equipment used in buildings includes boilers (oil and gas), furnaces (oil, gas, and electric), heat pumps, and space heaters. Boiler-based heating systems have steam and/or water piping to distribute heat. Boilers can be self-contained units, or they can be packaged units which are factory-built systems, disassembled for shipment, and reassembled at the site. The heated water may serve preheat coils in air handling units; reheat coils, and local radiators. Systems that circulate water or a luid are called hydronic systems. Heating water may also be used for heating of service water and other process needs, depending on the building type. Some central systems have steam boilers rather than hot water boilers because of the need for steam for conditioning needs (humidiiers in air-handling units) or process needs (sterilizers in hospitals, direct-injection heating in laundries and dishwashers, etc.). The remaining heating systems include heat pumps and space heaters that heat directly and require little or no distribution.

5.2 Mandatory Requirements The Code contains mandatory requirements for the following elements of the HVAC system: • • • • • • • •

5.2.1

Natural Ventilation Equipment Eficiency Controls Piping and Ductwork System Balancing. Condensers Economizers Hydronic Systems

Natural Ventilation

As per the Code: Natural ventilation (of buildings) shall comply with the design guidelines provided for natural ventilation in the National Building Code of India 2005,(NBC, 2005) Part 8, 5.4.3 and 5.7.1 These guidelines from NBC, 2005 have been reproduced below in Box 5-C, keeping in view the philosophy behind this Guide to include ECBC-referenced material in the Guide. However, the exact relevance of these general guidelines in the design of commercial buildings need to be critically examined.

Box 5-C: Design Guidelines for Natural Ventilation By Wind Action i. Building need not necessarily be oriented perpendicular to the prevailing outdoor wind; it may be oriented at any convenient angle between 0° and 30° without losing any beneicial aspect of the breeze. If the prevailing wind is from east or west, building may be oriented at 45° to the incident wind so as to diminish the solar heat without much reduction in air motion indoors. ii. Inlet openings in the buildings should be well distributed and should be located on the windward side at a low level, and outlet openings should be located on the leeward side. Inlet and outlet openings at high levels may only clear the top air at that level without producing air movement at the level of occupancy. iii. Maximum air movement at a particular plane is achieved by keeping the sill height of the opening at 85% of the critical height (such as head level) for the following recommended levels of occupancy: 1. For sitting on chair 0.75 m 2. For sitting on bed 0.60 m

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3. For sitting on loor 0.40 m

iv. v.

vi. vii.

viii.

ix. x. xi.

xii.

xiii. xiv. xv. xvi. xvii.

xviii. xix. xx.

Inlet openings should not, as far as possible, be obstructed by adjoining buildings, trees, sign boards or other obstructions or by partitions inside in the path of air low. In rooms of normal size having identical windows on opposite walls the average indoor air speed increases rapidly by increasing the width of the window up to two-thirds of the wall width; beyond that the increase is in much smaller proportion than the increase of the window width. The air motion in the working zone is maximum when window height is 1.1 m. Further increase in window height promotes air motion at higher level of window, but does not contribute additional beneits as regards air motion in the occupancy zones in buildings. Greatest low per unit area of openings is obtained by using inlet and outlet openings of nearby equal areas at the same level. For a total area of openings (inlet and outlet) of 20% to 30% of loor area, the average indoor wind velocity is around 30% of outdoor velocity. Further increase in window size increases the available velocity but not in the same proportion. In fact, even under most favorable conditions the maximum average indoor wind speed does not exceed 40% of outdoor velocity. Where the direction of wind is quite constant and dependable, the size of the inlet should be kept within 30 to 50% of the total area of openings and the building should be oriented perpendicular to the incident wind. Where direction of the wind is quite variable, the openings may be arranged so that as far as possible there is approximately equal area on all sides. Thus no matter what the wind direction is, there would be some openings directly exposed to wind pressure and others to air suction and effective air movement through the building would be assured. Windows of living rooms should open directly to an open space. In places where building sites are restricted, open space may have to be created in the buildings by providing adequate courtyards. In the case of rooms with only one wall exposed to outside, provision of two windows on that wall is preferred to that of a single window. Windows located diagonally opposite to each other with the windward window near the upstream comer give better performance than other window arrangements for most of the building orientations. Horizontal louvers, that is a sunshade, atop a window delects the incident wind upward and reduces air motion in the zone of occupancy. A horizontal slot between the wall and horizontal louver prevents upward delection of air in the interior of rooms. Provision of inverted L type (r) louver increases the room air motion provided that the vertical projection does not obstruct the incident wind. Provision of horizontal sashes inclined at an angle of 45° in appropriate direction helps to promote the indoor air motion. Sashes projecting outward are more effective than projecting inward. Air motion at working plane 0.4 m above the loor can be enhanced by 30% using a pelmet type wind delector. Roof overhangs help by promoting air motion in the working zone inside buildings. Verandah open on three sides is to be preferred since it causes an increase in the room air motion for most of the orientations of the building with respect to the outdoor wind. A partition placed parallel to the incident wind has little inluence on the pattern of the air low, but when located perpendicular to the main low, the same partition creates a wind shadow. Provision of a partition with spacing of 0.3 m underneath helps by augmenting air motion near loor level in the leeward compartment of wide span buildings. Air motion in a building unit having windows tangential to the incident wind is accelerated when unit is located at end-on position on downstream side. Air motion in two wings oriented parallel to the prevailing breeze is promoted by connecting them with a block on downstream side. Air motion in a building is not affected by constructing another building of equal or smaller height on the leeward side; but it is slightly reduced if the leeward building is taller than the windward block.

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xxi. Air motion in a shielded building is less than that in an unobstructed building. To minimize the shielding effect, the distances between two rows should be 8H for semi-detached houses and 10H for long rows houses. However, for smaller spacing the shielding effect is also diminished by raising the height of the shielded building. xxii. Hedges and shrubs delect the air away from the inlet openings and cause a reduction in indoor air motion. These elements should not be planted at a distance of about 8m from the building because the induced air motion is reduced to minimum in that case. However, air motion in the leeward part of the building can be enhanced by planting a low hedge at a distance of 2m from the building. xxiii. Trees with large foliage mass having trunk bare of branches up to the top level of window, delect the outdoor wind downwards and promotes air motion in the leeward portion of buildings. xxiv. Ventilation conditions indoors can be ameliorated by constructing buildings on earth mound having a slant surface with a slope of 10° on the upstream side. xxv. In case of industrial buildings the window height should be about 1.6m and the width about twothirds of wall width. These should be located at a height of 1.1m above the loor. In addition, openings around 0.9m high should be provided over two-thirds of the length of the glazed area in the roof lights. xxvi. Height of industrial buildings, although determined by the requirements of industrial processes involved, generally kept large enough to protect the workers against hot stagnant air below the ceiling as also to dilute the concentration of contaminant inside. However, if high level openings in roof or walls are provided, building height can be reduced to 4m without in any way impairing the ventilation performance. By Stack Effect Natural ventilation by stack effect occurs when air inside a building is at a different temperature than air outside. Thus, in heated buildings or in buildings wherein hot processes are carried out and in ordinary buildings during summer nights and during premonsoon periods, when the inside temperature is higher than that of outside, cool outside air will tend to enter through openings at low level and warm air will tend to leave through openings at high level. It would, therefore, be advantageous to provide ventilators as close to ceilings as possible. Ventilators can also be provided in roofs as, for example, cowl, ventpipe, covered roof and ridge vent. Energy Conservation in Ventilation System Maximum possible use should be made of wind-induced natural ventilation. This may be accomplished by following the design guidelines i. Adequate number of circulating fans should be installed to serve all interior working areas during the summer months in the hot dry and warm humid regions to provide necessary air movement at times when ventilation due to wind action alone does not afford suficient relief. ii. The capacity of a ceiling fan to meet the requirement of a room with the longer dimension D meters should be about 55D m3/min. iii. The height of fan blades above the loor should be (3H + W)/4, where H is the height of the room, and W is the height of the work plane. iv. The minimum distance between fan blades and the ceiling should be about 0.3 meters. v. Electronic regulators should be used instead of resistance type regulators for controlling the speed of fans. vi. When actual ventilated zone does not cover the entire room area, then optimum size of ceiling fan should be chosen based on the actual usable area of room, rather than the total loor area of the room. Thus smaller size of fan can be employed and energy saving could be achieved. vii. Power consumption by larger fans is obviously higher, but their power consumption per square meter of loor area is less and service value higher. Evidently, improper use of fans irrespective of the rooms dimensions is likely to result in higher power consumption. From the point of view of energy consumption, the number of fans and the optimum sizes for rooms of different dimensions are given in the following table:

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Table 5.1: Optimum Size/Number of Fans for Rooms of Diferent Sizes

Room Width

Room Length

m

4m

5m

6m

7m

8m

9m

10m

11m

12m

14m

16m

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

3

1200/1

1400/1

1500/1

1050/2

1200/2

1400/2

1400/2

1400/2

1200/3

1400/3

1400/3

4

1200/1

1400/1

1200/2

1200/2

1200/2

1400/2

1400/2

1500/2

1200/3

1400/3

1500/3

5

1400/1

1400/1

1400/2

1400/2

1400/2

1400/2

1400/2

1500/2

1400/3

1400/3

1 500/3

6

1200/2

1400/2

900/4

1050/4

1200/4

1400/4

1400/4

1500/4

1200/6

1400/6

1 500/6

7

1200/2

1400/2

1050/4

1050/4

1200/4

1400/4

1400/4

1500/4

1200/6

1400/6

1 500/6

8

1200/2

1400/2

1200/4

1200/4

1200/4

1400/4

1400/4

1500/4

1200/6

1400/6

1 500/6

9

1400/2

1400/2

1400/4

1400/4

1400/4

1400/4

1400/4

1500/4

1400/6

1400/6

1500/6

10

1400/2

1400/2

1400/4

1400/4

1400/4

1400/4

1400/4

1500/4

1400/6

1400/6

1 500/6

11

1500/2

1500/2

1500/4

1500/4

1500/4

1500/4

1500/4

1500/4

1500/6

1500/6

1 500/6

12

1200/3

1400/3

1200/6

1200/6

1200/6

1400/6

1400/6

1500/6

1200n

1400/9

1400/9

13

1400/3

1400/3

1200/6

1200/6

1200/6

1400/6

1400/6

1500/6

1400/9

1400/9

1 500/9

14

1400/3

1400/3

1400/6

1400/6

1400/6

1400/6

1400/6

1500/6

1400/9

1400/9

1500/9

Source: National Building Code of India 2005. For data on outdoor wind speeds at a place, reference may be made to “The Climatic Data Handbook prepared by Central Building Research Institute, Roorkee, 1999.” Box 5-D provides additional information in naturally ventilated spaces for tropical countries.

Box 5-D: Optional Method for Determining Acceptable Thermal Conditions in Naturally Conditioned Spaces Based on Field Experiments Conducted in Tropical Countries The adaptive model of thermal comfort is derived from a global database of 21,000 measurements taken primarily in ofice buildings in the tropical climate. The allowable operative temperature limits may not be extrapolated to the outdoor temperature above and below the end points of the curves in this igure. If the mean monthly outdoor temperature is less than 10°C or greater than 33.5°C, this option may not be used. Occupant-controlled naturally conditioned spaces are those spaces where the thermal conditions of the space are regulated primarily by the occupants through opening and closing of windows. Field experiments have shown that occupants’ thermal responses in such spaces depend in part on the outdoor climate and may differ from thermal responses in buildings with centralized HVAC systems primarily because of the different thermal experiences, changes in clothing, availability of control, and shifts in occupant expectations. This optional method is intended for such spaces. In order for this optional method to apply, the space must be equipped with operable windows that open to the outdoor and that can be readily opened and adjusted by the occupants of the space. Mechanical ventilation with unconditioned air may be utilized, but opening and closing of windows must be the primary means of regulating the thermal conditions in the space. The space may be provided with a heating system, but this optional method does not apply when a heating system is in operation. It applies only to spaces where the occupants are engaged in near sedentary physical activities, with metabolic rates ranging from 1.0 met to 1.3 met1. This optional method applies only to spaces where the occupants may freely adapt their clothing to the indoor and/or outdoor thermal conditions. Limits on Temperature Drifts and Ramps Time Period Maximum Operative Temperature Change Allowed

0.25h

0.5h

1h

2h

4h

1.1° C (2.0°F)

1.7°C (3.0°F)

2.2°C (4.0°F)

2.8°C (5.0°F)

3.3°C (6.0°F)

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Figure 5.1: Acceptable operative temperature ranges for naturally conditioned spaces. Allowable indoor operative temperature for spaces that meet these criteria may be determined from the igure above. This igure includes two sets of operative temperature limits —one for 80% acceptability and one for 90% acceptability. The 90% acceptability limits may be used when a higher standard of thermal comfort is desired. 1 1met=

58W/m2 : for typical ofice activity, one person is likely to produce 100- 125 watts of heat.

Source: ASHRAE 55, 2004.

5.2.2

Minimum Equipment Eiciencies

Minimum equipment eficiencies are required to be met for all HVAC equipment. These include chillers, unitary air conditioner, split air conditioner, packaged air conditioner, and boilers. Box 5-E and Box 5-F provide basic information and an overview of air conditioning systems. Box 5-G provides more information on Chillers.

Box 5-E: Type of Air-Conditioning Systems There are primarily two main types of air conditioning systems: 1. A direct expansion or “DX” type system in the form of room air conditioners, split system air conditioners and packaged air conditioners. Heat exchange takes place directly from the refrigerant within the copper tubes to the air being drawn across the inned coil by an evaporator fan. The DX type systems offer localized solutions for a building’s heating and cooling needs. These systems are typically appropriate for smaller (single-zone) buildings. 2. Central plant system uses chilled water recirculation. Compared to a DX systems, a central plant HVAC will be able to provide better thermal comfort and lexibility. Direct Expansion Systems or DX Systems

Unitary air conditioners: These are normally used for cooling individual rooms and provide cooling only when needed. Room air conditioners house all the components of an air conditioning system discussed above in one casing. Their eficiency is generally lower than that of central plant systems. Split-system air conditioning systems: This consists of an outdoor metal cabinet that contains the condenser and compressor, and an indoor cabinet that contains the evaporator. In many split-system air conditioners, this indoor cabinet also contains a furnace or the indoor part of a heat pump. Packaged air conditioners: In a packaged air conditioner, the evaporator, condenser, and compressor are all located in one cabinet, which usually is placed on a roof or on a concrete slab adjacent to the building. This type of air conditioner is typical in small commercial buildings and also in residential buildings. Air supply and return ducts come from indoors through the building’s exterior wall or roof to connect with the packaged air conditioner, which is usually located outdoors. Packaged air conditioners often include electric heating coils or a natural gas furnace. This combination of air conditioner and central heater eliminates the need for a separate furnace indoors. Energy Conservation Building Code (ECBC) User Guide

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Central Plant Systems

Central plant air conditioning systems: In central air-conditioning systems, chilled water is generated via a central chilled water plant. The chilled water is distributed to air-handling units or fan-coil units via a chilled water reticulation system consisting of chilled water pipes, valves, ittings, and pumps. The chillers used in central chilled water plants include air-cooled chillers as well as water-cooled chiller systems that work in conjunction with cooling towers for heat rejection. Box 5-F provides an overview of the differences between DX and Central HVAC systems. It should help in selecting appropriate system for the building.

Box 5-F: Overview of DX and Central Plant HVAC Systems Central Chilled Water Systems Building Space Will require separate building space to house the chillers, Requirements boilers, pumps, AHU’s, distribution networks and control panels. In addition, space is required outdoors for condensing unit for air-cooled machines and cooling tower for water-cooled machines.

Direct Expansion or “DX” Systems No separate plant room space is required as the refrigeration package is integral to the package unit/condensing unit which is generally located outdoors. Evaporator units are generally located indoors.

The building structure should be designed to take the weight of equipment. Suitable vibration control must be considered and adequate load bearing beams and columns must be available for lifting and shifting of such equipment.

The local systems are smaller in size and are less bulky.

Aesthetics

Central systems are generally designed as concealed systems and the visible distribution grilles etc. can be easily blended with the aesthetics.

The appearance of local units can be unappealing and may not necessarily blend well with the aesthetics.

Zoning

Central HVAC system may serve multiple thermal zones and have their major components located outside the zone(s) being served, usually in some convenient central location. This system can provide better lexibility in terms of zoning.

A local HVAC system typically serves a single thermal zone and has its major components located within the zone itself or directly adjacent to the zone. Multiple units are required for multiple zones. This system is less lexible to zoning requirements.

Air Quality

Controls

The quality of air conditioning is comparatively superior, The air quality is not comparable to central with better control over temperature, relative humidity, air systems. These systems typically cannot provide iltration, and air distribution. close humidity control or high eficiency iltration. Best suited for applications demanding close control of temperature, humidity, and cleanliness and can be customized The compact systems, being standard factory as per the design conditions. items, typically cannot be modiied to suit the required design conditions all the times. Central HVAC systems will require a control point for each thermal zone. The controls are ield wired and are integrated to a central control panel. The controls are complex and depend on the type of system.

Local units are off-shelf items complete with integrated controls. They usually have a single control point which is typically only a thermostat.

Constant air volume (CAV) systems alter the temperature while keeping the constant air delivery. CAV systems serving multiple zones rely on reheat coils to control the delivered cooling. This incurs a lot of energy wastage due to simultaneous cooling and heating.

The room-by-room or “zone” control minimizes over cooling typical of central air-conditioning systems. With the zone-control ability of the compact systems, only occupied spaces are maintained at a comfort level, and conditioning for the rest of the building is turned down or Space temperature control can also be achieved by applying shut off. a variable air volume (VAV) system, which primarily alters the air delivery rates. The VAV system may or may not have It should be noted that some DX systems have a reheat coil, which provides additional heat when the space limited capacity control and have limited capability does not need to be cooled or needs less cooling than would to reduce airlow during low load situations. be delivered by supply air at the terminal box’s minimum air Hence, there is a limitation in saving fan energy quantity setting. in DX systems with some types of DX systems only having on/off control for the compressors Proper zoning using “face zoned” AHUs working in that can result in considerable hunting and space conjunction with downstream VAV boxes will provide temperature luctuation. energy-eficient cooling and eliminate the need of reheat.

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Heating, Ventilation and Air Conditioning

Eficiency

Central systems usually operate under part load conditions, In a building where a large number of spaces and localized areas cannot be isolated for complete shut may be unoccupied at any given time, such as a down under any condition. dormitory or a motel, local systems may be totally shut off in the unused spaces, thus providing In a central system, the individual control option is not huge energy saving potential. always available. If individual control is desired, the system shall be designed as variable air volume system with localized As a self-contained system, a local HVAC system may provide greater occupant comfort through thermostats. totally individualized control options -- if one Central systems designed for VAV system is based on block room needs heating while an adjacent one needs load calculations, as the VAV units allow the system to cooling, two local systems can respond without borrow air from areas with low load. By incorporating VAVs conlict with variable speed drive on air handling units, it is possible As the compact systems are small, they are to achieve excellent savings in power. designed for full peak load and the standard Proper zoning as mentioned earlier can avoid conlicting rooftop or package units are not typically demands for heating and cooling. available with variable speed option. This type of system therefore has very limited potential to operate eficiently during part load situations. The availability of VRF system is changing this.

Refrigerant Containment

Central plant systems provide an excellent means to contain all refrigerant within the chiller housing and plant room. It is possible to detect any minor leaks within the localized plant room and take remedial action to arrest the leak.

Operations and Maintenance (O&M)

Large central systems can have a life useful life of up to 25 Local systems can have a useful life of up to 15 years. years.

Cost

Unlike central systems, DX systems pose a greater risk of refrigerant leaks to the atmosphere. With DX systems installed in several localized areas it may be very dificult or impossible to detect these leaks, especially in split systems with long pipe runs using high pressure refrigerant.

Central systems allow major equipment components to be Local systems maintenance may often be kept isolated in a mechanical room. Grouping and isolating relatively simple but maintenance may have to key operating components allows maintenance to occur with occur directly in occupied spaces. limited disruption to building functions. The initial purchasing and installation cost of a central air conditioning system is much higher than a local system.

Packaged and split units have much lower irst costs than a central system.

These systems can offer higher system eficiencies (full load and part load) and thus, can pay pack the elevated initial costs through reduced costs of operations within a few years.

The operating costs of unitary systems is usually higher due to lower eficiency ratings and lower part load performance values

Extra cost beneits can be achieved due to the potential for energy eficiency measures like thermal heat recovery, economizers, energy storage systems and etc.

The potential for adoption of high-tech energy eficiency measures is very limited

Source: A. Bhatia, Course Content (PDH 149), HVAC Design Aspects: Choosing A Right System-Central V/s Compact Systems. http://www.pdhcenter.com/Heating System Types, and Team Catalyst The Code refers to various types of chillers; Box 5-G gives a brief description of the chillers.

Box 5-G: Chiller What is a Chiller? A chiller is essentially a packaged vapor compression cooling machine. The chiller rejects heat either to condenser water (in the case of a water-cooled chiller) or to ambient air (in the case of an air-cooled chiller). Water-cooled chillers incorporate the use of cooling towers, which improve heat rejection more eficiently at the condenser than air-cooled chillers. For a water-cooled chiller, the cooling tower rejects heat to the environment through direct heat exchange between the condenser water and cooling air. For an air-cooled chiller, condenser fans move air through a condenser coil. As heat loads increase, water-cooled chillers are more energy-eficient than air-cooled chillers. A typical chiller is rated between 15 to 1000 tons (53 to 3,500 kW) in cooling power.

Energy Conservation Building Code (ECBC) User Guide

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Heating, Ventilation and Air Conditioning

What are the different types of chillers? Chillers are classiied according to compressor type. Electric chillers for commercial comfort cooling have centrifugal, screw, scroll, or reciprocating compressors. Centrifugal and screw chillers have one or two compressors. Scroll and reciprocating chillers are built with multiple, smaller compressors. • Centrifugal chillers are the quiet, eficient, and reliable workhorses of comfort cooling. Although centrifugal chillers are available as small as 70 tons, most are 300 tons or larger. • Screw chillers are up to 40% smaller and lighter than centrifugal chillers, so are becoming popular as replacement chillers. • Scroll compressors are rotary positive-displacement machines, also fairly new to the comfort cooling market. These small compressors are eficient, quiet, and reliable. Scroll compressors are made in sizes of 1.5 to 15 tons. The energy eficiency of cooling and heating systems in terms of Coeficient of Performance (COP), Energy Eficiency Ratio (EER) and Integrated Part-Load Value as speciied by the Code are presented in Box 5-H

Box 5-H: Energy Eiciency Terms Coeficient of Performance (COP) – Cooling The ratio of the rate of heat removal to the rate of energy input, in consistent units, for a complete refrigerating system or some speciic portion of that system under designated operating conditions Coeficient of Performance (COP) – Heating The ratio of the rate of heat delivered to the rate of energy input, in consistent units, for a complete heat pump system, including the compressor and, if applicable, auxiliary heat, under designated operating conditions Energy Eficiency Ratio (EER) The ratio of net cooling capacity in BTU/hr to total rate of electric input in watts under designated operating conditions. Integrated Part-Load Value (IPLV) A single number igure of merit based on part-load EER, COP, or KW/ton expressing part-load eficiency for air-conditioning and heat pump equipment on the basis of weighted operation at various load capacities for the equipment. As per the Code: Cooling equipment shall meet or exceed the minimum eficiency requirements presented in Table 5.2. Heating and cooling equipment not listed here shall comply with ASHRAE 90.1-2004 §6.4.1. Table 5.2: Chillers

Equipment Class Air Cooled Chiller